dirdiff: Move file status filters to GSettings
vcview: Move file status filters to GSettings
meldapp: Clean up GAction initialisation slightly
preferences: Migrate filter settings to GSettings
dirdiff: Migrate column ordering and visibility to GSettings
preferences: Update font preference handling to use GSettings
meldwindow: Move toolbar and statusbar visibility handling to GSettings
filediff: Move draw-spaces handling into GSettings
preferences: Update text encoding setting, and remove its UI

People really shouldn't be using this as it is. In the near future
there will be a file selector with encoding selection, and that should
fix almost all cases. For the rest, this preference isn't hard to
change via dconf.
preferences: Move ignore-blank-lines to GSettings
preferences: Update word wrapping setting to use GSettings
vcview: Update VC console visibility setting to GSettings
preferences: Move VC file order setting to GSettings
preferences: Move timestamp preference widget to builder-based creation
preferences: Clean up filter import
preferences: Remove now-unused prefs arg
preferences: Clean up relative imports
preferences: Update copyright notice
meldwindow: Move window size to GSettings
meld: Add awful hack to compile gschemas at runtime if they're missing